Karin Hammar Fab 4 is a jazz quartet led by trombonist and composer Karin Hammar. Since its formation in 2014, the group has released two critically acclaimed CDs (2016 and 2018) exploring the format of trombone, guitar, bass and drums. The group has achieved great success in both the Swedish and international press and tours internationally on a regular basis. Karin Hammar Fab 4 has been reviewed in the prestigious jazz magazine Down Beat and boasts a Spotify hit (Uphill) with over 6 million streams.

Prior to the group's third CD entitled Strings Attached, Karin Hammar composed music for the unique setting of jazz quartet plus string quartet featuring harmonica soloist. The idea for Strings Attached was born on a trip to Tel Aviv in 2018 during which Karin performed with French harmonica virtuoso Olivier Ker Ourio.

Ourio, originally from the French Reunion Islands and currently based in Paris, is one of France's most sought-after jazz soloists and band leaders and considered by the international jazz press to be Toots Thieleman's successor. Strings Attached was recorded in early 2020 at Nilento Studios in Gothenburg, Sweden and is scheduled to be released on Prophone/Naxos in September 2020.

Karin Hammar Fab 4:
- Karin Hammar (trombone, compositions)
- Andreas Hourdakis (guitar)
- Niklas Fernqvist (double bass)
- Fredrik Rundqvist (drums)

The Fab Stringz:
- Hanna Helgegren (violin)
- Karin Liljenberg (violin)
- Jill Johansson (viola)
- Anna Wallgren (cello)